1. Field of the Invention
The present invention relates generally to power tools for treating and shaping concrete. More particularly, the present invention relates to portable, hand operated power tools for shaping green concrete into curbs.
2. Description of the Related Art
Concrete curbs form structural borders upon peripheries of concrete streets or parking lots where aesthetics are important. Appropriate concrete curbing is often integral with gutter structures that contribute to proper drainage. Additionally, residential property owners often employ decorative edging along borders to enhance the appearance of their landscaping. Properly formed curb and gutter designs add valuable structural and functional attributes to modern concrete structures as well. In many communities properly designed curbs and gutter arrangements are required by zoning ordinances.
A wide variety of curb forming techniques thus exist. Concrete shaping systems and curb forming devices can contact freshly placed concrete directly, while still green in a slab, or concrete curbing can be extruded with a variety of placement devices.
Some large scale, motor driven curb forming devices store concrete in a hopper, and pump it outwardly through shaping dies, molds or extruder equipment that preshapes the curb. Some larger, wheeled systems used to strike-off or screed large slabs traverse forms or rails for support. Many include ancillary curb installers that shape slab edges as concrete is laid.
So-called slip-forming machines have been adapted to lay concrete curbing or curb and gutter arrangements during slab pouring and screeding. Typical slip forming machines follow the length of the slab and store wet concrete in a hopper. Concrete discharged from or forced out of the hopper is shaped by a form proximate the hopper that moves with the machine. As the form compresses and shapes the concrete edges, a properly shaped curb or curb and gutter combination is formed in place.
For example, U.S. Pat. No. 4,544,346 issued Oct. 1, 1985 illustrates curb forming apparatus associated with a screed. The screed treats plastic concrete and forms a curb along one or both sides of the slab as the screed travels the slab length. The triangular truss concrete screed has first and second sides supported by rollers which engage spaced apart forms. The screed traverses the entire width of the slab, and is supported upon forms, and is not hand operated by a single worker. A curb form is coupled to one side of the finishing machine.
U.S. Pat. No. 4,217,065 issued Aug. 12, 1980 discloses a slip-form curb and gutter machine with a wheeled chassis that travels along tracks. A concrete receiving hopper discharges green concrete that is shaped by suitable forms affixed to the chassis. A hand winch above the hopper attaches to a cable for pulling the machine along its tracks. An operator can stand on a platform disposed above the form.
U.S. Pat. No. 5,803,656 issued Sep. 8, 1998 discloses a motorized concrete screed with a roller attached to a chassis. A pair of handles extending from the chassis are independently adjustable. A throttle attached to one of the handles is electrically connected to the motor. A pair of wheel assemblies permit the apparatus to be easily moved to and from a worksite without damaging the roller.
Slip-form machines and large screeding devices involve expensive, heavyweight equipment, and they are too expensive and cumbersome for smaller contractors to set up and use economically, particularly on smaller jobs. Because of the disadvantages with large slip form machines and screeds, smaller hand operated machines have evolved for treating concrete and shaping it into gutters or curbs. Some use motor driven carriages that, like slip form machines, include hoppers that discharge concrete into molds or shapers that compress the concrete into a desired shape. Some analogous devices use a U-shaped handle arrangement, that journals a rotatable roller whose periphery contacts the concrete for shaping.
For example, U.S. Pat. No. 3,910,738 issued Oct. 7, 1975 discloses a concrete finishing roller rotatably mounted on an axle that is controlled by a handle. Indicia formed on the outer periphery of the roller imprints the concrete surface. Workers can manipulate the handle so that the roller may be pushed across green concrete. The depth of the impression made in the concrete surface may be varied by the addition or the removal of weights on the handle and by vibrating the roller in a vertical plane as it moves across the concrete surface.
U.S. Pat. No. 5,354,189 issued Oct. 11, 1994 discloses a concrete forming device for extruding curb, barrier, wall, gutter or the like from concrete or cement. Cement stored within a vibrating hopper falls onto tapered, counter rotating augers which compact and force the concrete through an adjacent extrusion mold for shaping.
U.S. Pat. No. 5,846,176 issued Dec. 8, 1998 also shows a hand-operated roller tool for concrete finishing. A hollow, cylindrical, roller secured journalled to a U-shaped frame has protrusions or nubs defined about its outer surface to produce a desired texture on the green concrete. A single worker can operate the device with a handle coupled to the frame.
U.S. Pat. No. 6,474,906 issued Nov. 5, 2002 discloses a concrete finishing machine wherein a roller extends between a primary motorized unit and a secondary unmotorized unit disposed on each side of a slab to be paved. An engaging lever must be pressed to initiate tube rotation, driving the primary and secondary units forward.
U.S. Pat. No. 6,863,470 issued Mar. 8, 2005 provides a curbing apparatus for shaping green concrete by pushing it through a channel defined by a mold.
U.S. Pat. Application No. 20020021938 published Feb. 21, 2002 discloses a curb forming and extruding machine includes a plunger that forces raw concrete via lower hopper into and through a curb extrusion mold.
U.S. Pat. No. 7,621,694 issued Nov. 24, 2009 discloses a curb forming machine using a single, rotatable curb-forming roller. A handle assembly is utilized for pulling and maneuvering the roller, and a motor rotates the roller to shape and smooth wet concrete into curbing.
U.S. Pat. No. 5,449,406 issued Sep. 12, 1995 discloses a machine for applying grout mortar to a tiled surface. A frustroconical shroud having a plurality of generally radially extending blades rotates about an axis that is perpendicular to the surface being treated.
U.S. Pat. Application No. 20050238745 discloses an apparatus for impressing three-dimensional patterns in a slip-formed concrete wall. Impression rollers include outer peripheries provided with three-dimensional patterns. One roller coats a side of an exposed wall, and an ancillary roller coats the top of the wall.
Despite the advantages of relatively recently develop portable curb forming devices, they suffer from well known disadvantages. Often they have to be made flush with available forms, and hand controlled designs with large rollers are difficult to guide and control. Irregular patterns and misshapen concrete edges can thus result. Changing the operating direction is difficult, because handles and frames, including wheeled carriages where used, are designed to move in only one direction. Further, where rollers are placed horizontally to help propel the apparatus, and rotate in an axis parallel with the plane of the slab, curb deformation and uneven spots can occur when the unit suddenly jerks in response to tight turns in smaller pours.